In an apparatus for recording electrophotographic images which forms a full-color image or a monochromatic image, there are installed around the photoreceptor drum, for example, a charging device for the photoreceptor drum, the an image exposing means for exposing an image on the photoreceptor drum, a developing device for developing the electro-static image on the photoreceptor drum with a toner, a transfer device for transfering the toner image on photoreceptor drum to the recording paper, etc.
Among the above, the developing device in the full-color image apparatus for recording electrophotographic image consists of three developing devices, respectively storing yellow (Y), Magenta (M) and Cyan (C) toner, and arrangements are so made that a full-color image can be obtained by forming each toner image of Yellow (Y), Magenta (M), Cyan (C) on the photoreceptor drum, while the photoreceptor drum makes 3 revolutions, and by transfering those toner images to the recording paper.
In such full-color image apparatus for recording electrophotographic images, perfect conditions of having a correct mixing ratio among each toner of Yellow (Y), Magenta (M), Cyan (C) cannot always be obtained. Therefore, in specially attempting to obtain a black image, there are cases where a clear black image cannot be obtained by having the black image reddish or bluish.
Therefore, in order to obtain clear black image, developing with Black (BK) toner is conducted, by providing a developing device storing Black (BK) toner, in addition to Yellow (Y), Magenta (M), Cyan (C) toners, and not by mixing 3 colors of Yellow (Y), Magenta (M), Cyan (C).
However, since a developing device storing Black (BK) toner, in addition to Yellow (Y), Magenta (M), Cyan (C) toners, has to be provided, there is a problematic point that the apparatus tends to be of large-size.
Therefore, there is stated in the Japanese Patent Publication Open to Public Inspection No. 72159/1983 an image forming apparatus of transfering drum type, where there is provided an exclusive black-and-white image unit, having a photoreceptor drum, a corona charging device which makes the photoreceptor drum surface charged uniformly, a developing device and a cleaning device as an integrated unit, wherein the unit is detachably mounted on the apparatus body and alternately interchanged with such unit, an exclusive color image unit, having the photoreceptor drum, a corona charging device, the developing device for color images, in which Yellow developing device, Magenta developing device and Cyan developing device are sequentially installed in the rotating direction of photoreceptor drum, and the cleaning device as an integrated unit of mountable construction. Further, in the patent publication, there is also stated that when either one of the above two units is mounted on the apparatus body, the control circuit for obtaining color copying or the control circuit for obtaining black-and-white copying can be selected automatically.
However, automatic selection of the image forming conditions as stated in the Japanese Patent Publication 0.P.I. No. 72159/83 is determined according to the number of combination between the protrusion on the unit side and the microswitch on the body side or according to the resistance value by electrical connection between the pin on the unit side and the jack on the body side. Such detection means will require mechanical precision of each part and will pose problems of malfunction due to fault in such parts. Particularly, when there are a large number of unit types, it becomes difficult to determine by the resistance value. In the type which uses microswitches, there is a problem of requiring arrangement of a large number of microswitches.
The use of color copier and color printer is quite diversified, and user requirements are also diversified. In particular, the color of toners used, the combination of colors, and consumption of toner have become very varied, thereby making it difficult to provide an apparatus for recording color image to satisfy all of the requirements, as a general-purpose equipment.
In order to solve this problem, providing a recording apparatus body for common use has been made and recording of several colors has been made possible, to which various process cartridges, each having a developing unit which stores plural kinds of toners, are replaceably mounted. However, in this case, it is very cumbersome for an operator to have the information on various combinations of the color toner to be stored in the recording apparatus body in advance and to operate it according to the indication every time when the processing cartridge is replaced. This will also increase possibilities of faulty indication and faulty operation.